Try this :- https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars

This may help you . Let us know if this work !

Sounds like you have two folders that are labeled Bookmarks Toolbar, which happens when you "import" from a bookmarks.html file. "Import" appends the existing bookmarks that are in Firefox; doing a "Restore" of a json backup would have replaced any existing bookmarks with those that are in the json backup backup file.

You need to "rearrange" the bookmarks that are in the lower Bookmarks Toolbar folder (the bookmarks that you imported) and get those bookmarks into the current Bookmarks Toolbar folder, which is at the top of the list.

https://support.mozilla.org/en-US/kb/sort-bookmarks-quickly-find-ones-you-want#w_rearranging-manually

Your reply didn't answer my question, Deb, but it did give me some other info I needed. Thank you for taking the time to reply.

Thank you Edmeister! Your reply told me exactly what I needed to do. I simply cut the contents of the duplicate Bookmarks Toolbar at the bottom of the list of bookmarks and pasted it into the original Bookmarks Toolbar at the top of the list of bookmarks. I then deleted the duplicate Bookmarks Toolbar folder, and all is well again. Those toolbar folders showed up at the top of the page in the Bookmarks Toolbar, and everything's back where it belongs.

BTW, what is json and the json backup backup file? Thanks!